Hydrocarbon drilling systems use drilling fluid or mud for drilling a wellbore in a subterranean earthen formation. In some applications, drilling systems include a blowout preventer (BOP) configured to control the inlet and outlet of fluid from the wellbore, and particularly, to confine well fluid in the wellbore in response to a “kick” or rapid influx of formation fluid into the wellbore. An individual BOP stack may include both ram BOPs and annular BOPs. Annular BOPs are configured to close or seal against the outer surface of a drill string extending through the BOP stack.
In some applications, annular BOPs include a hydraulic assembly or package for actuating between an open position allowing for fluid flow in an annulus disposed between the drill string and the annular BOP, and a closed position restricting fluid flow through the annulus. The hydraulic package may include one or more seals for sealing against an outer housing of the annular BOP, where engagement from the outer housing compresses the one or more seals to provide a sealing engagement therebetween. In some applications, engagement between the one or more seals of the hydraulic package and the outer housing increases the difficulty of inserting the hydraulic package into, and removing it from, the outer housing. Particularly, sealing engagement provided by the one or more seals may necessitate using a relatively large amount of force to properly seat the hydraulic package within the outer housing when installing the hydraulic package therewithin.